The present invention relates to a method of producing a resin mold which is one kind of easy-to-use mold.
As molds used for molding resins, there have been generally used metal molds, and in some cases, for example, for trial production or small-quantity production, there have been used resin molds of a type in which a plane facing to a cavity is made from a resin.
For example, a method of producing a resin mold has been described in Japanese Patent Laid-open No. 2001-105438 entitled xe2x80x9cMethod of Producing Resin Moldxe2x80x9d. FIGS. 7, 9 and 10 in this document are recited in the following figures.
FIGS. 16(a) to 16(c) are views showing a related art resin mold and a production method thereof described in the above document, wherein FIGS. 16(a), 16(b) and 16(c) are recited from FIGS. 10, 7, and 9 of the above document, respectively. It is to be noted that in FIGS. 16(a) to 16(c), all of parts are denoted by new reference numerals.
FIG. 16(a) is a sectional view of a finished resin mold. A resin mold 100 is composed of a front side mold part 101 and a back side mold part 102. The front side mold part 101 includes a reinforcing member 103 to which a resin layer 104 is provided, and the back side mold part 102 includes a reinforcing member 105 to which a resin layer 106 is provided. A cavity 107 is formed between the resin layers 104 and 106. Accordingly, the resin mold 100 is a mold of a type in which a plane facing to a cavity is made from a resin. A method of producing such a resin mold 100 will be described with reference to FIGS. 16(b) and 16(c).
In the step shown in FIG. 16(b), a master model 110 including clamping lug portions 111 and 112 is clamped between the reinforcing members 103 and 105, and resins 115 and 116 are injected in mold surface forming spaces 113 and 114, respectively.
In the step shown in FIG. 16(c), after the resins 115 and 116 are cured to form the resin layers 104 and 106, the reinforcing members 103 and 105 are separated from each other, to remove the master model 110. By assembling the reinforcing members 103 and 105 in the state that the master model 110 has been removed, the resin mold 100 shown in FIG. 16(a) is obtained.
Referring to FIG. 16(c), as the master model 110, there has been generally used a rapid prototyping model produced by a rapid prototyping process advantageous in easy production. The rapid prototyping model, however, is poor in rigidity, to be thus easily deflected.
As described above, the resins 115 and 116 are injected in the mold surface forming spaces 113 and 114, respectively, in the step shown in FIG. 16(b). In this step, a deviation of injection timing or the like inevitably occurs, to deflect the master model 110 rightwardly or leftwardly. To prevent such deflection of the master model 110, supporting members 117 and 118 are inserted as shown in the figure; however, portions, apart from these supporting members 117 and 118, of the master model 110 are defected. If the master model 110 is deflected, the shape of the cavity 107 shown in FIG. 16(a) becomes inaccurate, with a result that the finishing accuracy of a molded product is degraded.
An object of the present invention is to provide a method of producing a resin mold, which is capable of preventing a master model from being deflected.
To achieve the above object, according to an invention described in claim 1, there is provided a method of producing a resin mold, characterized by including the steps of preparing a master model having a shape corresponding to a product shape and including a clamping lug portion at a periphery of the master model, and a first back surface reinforcing member and a second back surface reinforcing member; clamping the master model between the first and second back surface reinforcing members in a state that a first resin filling space is kept between the master model except the clamping lug portion and the first back surface reinforcing member and a second resin filling space is kept between the master model except the clamping lug portion and the second back surface reinforcing member; filling the first resin filling space with a temporary filler, the temporary filler being adapted to be easily injected in or discharged out of the first resin filling space; filling the second resin filling space with a resin as a material of the resin mold, and curing the resin; discharging the temporary filler from the first resin filling space; filling the first resin filling space with a resin as a material of the resin mold, and curing the resin; and removing the master model.
The back surface of the master model is supported by the temporary filler having been injected to fill the first resin filling space. In such a state, a resin as a material of the resin mold is injected to fill the second resin filling space. Subsequently, in the state that the back surface of the master model is supported by the resin having been injected to fill the second resin filling space, a resin as a material of the resin mold is injected to fill the first resin filling space. In this way, at the time of filling the space with a resin as a material of the resin mold, since the back surface of the master model is supported by the temporary filler or the resin as a material of the resin mold having been injected to fill the opposed space, the master model is prevented from being deflected. As a result, it is possible to obtain a cavity with a high accuracy, and hence to obtain a molded product having a desirable shape.